The present invention relates generally to an apparatus for controlling the temperature in a coolant circulating system of an internal-combustion engine, such as a motor vehicle engine, of the type containing a thermostatic valve that controls the coolant flow from the internal-combustion engine through a direct return flow line and/or through a heat exchanger back to the internal-combustion engine. More particularly, the present invention relates to thermostatic controls responsive to coolant and motor temperatures as well as external parameters, such as the temperature of the outside environment.
It has long been known to use thermostatic valves for controlling the coolant or cooling water temperature of an internal-combustion engine. These thermostatic valves are adjusted in such a way that, as the engine is started at a certain temperature below the optimum operating temperature, the coolant flow connection to the heat exchanger is opened up only after a predetermined temperature is achieved by the coolant. Until this predetermined temperature is achieved, coolant flow into the engine is only through the direct return flow line. The object of these arrangements is for the internal-combustion engine to be heated or warmed-up to its optimum operating temperature in as short a time as is possible.
The outside environment temperature has considerable influence on the engine warming-up time. In the case of a high outside temperature, the optimum operating temperature of the internal-combustion engine will be reached far faster than in the case of a lower outside temperature. A thermostatic valve that opens at a coolant temperature that is too far below the optimum operating temperature delays achievement of the optimum operating temperature of the internal combustion engine, especially in the case of low outside temperatures. For low outside temperatures, it is therefore desirable that the thermostatic valve open at a higher coolent temperature that is closer to the optimum operating temperature. However, in the case of high outside temperatures, it is desirable that the thermostatic valve open at a clearly lower coolant temperature so that, subsequently, the optimum operating temperature of the engine will not be exceeded.
In prior practice, the selection of a single opening temperature of the thermostatic valve has represented a compromise which, as much as possible, must take into account all outside temperatures. In the manufacturing plant this opening temperature is typically adjusted via a counterbearing which is then secured in the adjusted position. For example, the device shown in German Published Unexamined Application (DE-OS) 25 32 057 provides a valve having a working piston with an external threaded portion and screwed into a nut serving as a counterbearing. This nut is kept stationary in a strap. After adjusting the nut to provide the desired opening temperature, the nut is secured in that position on the threaded portion by, for example, a counternut or calking of the thread. Once so screwed, the thermostatic valve is not responsive to variations in the outside temperature.
However, in practice it has been found to be desirable to construct a thermostatic valve in such a way that it is responsive to variations in outside temperatures, i.e., that in the case of low outside temperatures it opens at a higher coolant temperature than in the case of high outside temperatures. In an attempt to achieve this, it has been suggested that so-called thermostatic winter valves be installed for low outside temperatures, and so-called thermostatic summer valves be installed for higher outside temperatures. However, this results in an additional maintenance procedure and, especially when the thermostatic valve is not selected correctly, in the danger of damaging the engine.
In order to provide a thermostatic valve responsive to outside temperatures it has also be suggested to employ a single valve device that can be adjusted to the respective existing outside temperature. However, none of the previously known devices of this type have been used in practice since they are all special constructions that deviate from the proven constructions for thermostatic valves, require high manufacturing expenditures and also do not offer sufficient operational reliability. For example, the device shown in German Published Unexamined Application (DE-OS) 14 51 669 provides two thermostatic working elements which are to be used individually or, alternatively, successively. The relative position of these two thermostatic working elements is changed individually or jointly with respect to the valve disk, requiring relative motion between the thermostatic working element and the valve disk. In addition to requiring high cost expenditures, this device presents the problem that a slideway must be provided between the valve disk and the thermostatic working elements, such a slideway is very susceptible to interferences and is located where it is difficult to ensure tightness over an extended operating period.
U.S. Pat. application Ser. No. 510,192, filed on July 1, 1983, now U.S. Pat. No. 4,522,334 and assigned to the assigner of the present invention, provides a device wherein the position of the abutment stop can be changed in such a way that it forms different support points for the working piston so that the distance to the valve plate housing can be adjusted. This device does not require any basic change of the valve construction that has proven itself in practice. In addition, it is possible, by means of this device, to not only carry out a control that is dependent on the outside temperature but also to use other control variables in order to adjust the operating temperature of the engine, such as the exhaust gas temperature, the speed and/or the torque of the engine, the vacuum in the suction pipe, the pressure difference at a vacuum cell, the oil temperature, or similar variables. While this arrangement has been successful in many applications, it is desirable to provide a faster and less expensive control means.
It is therefore an object of the present invention to provide an improved thermostatic valve having valve characteristics responsive to changes in external parameters and a reduced cost of assembly and maintenance.
Another object is to provide a thermostatic valve for use in coolant circulating systems of internal-combustion engines which is quickly responsive to control parameters.
A further object is the provision of a simplified and efficient thermostatic valve assembly for rendering thermostatic valves responsive to external parameters.
These and other objects of the present invention are achieved by the provision of a thermostatic valve containing a thermostatic working element having a housing supporting a valve disk and a working piston extending and being supported at a counterbearing such that the working piston and counterbearing form an adjusting mechanism. A control element is provided in connection with the working piston or the counterbearing which forces the working piston into an adjusted position. This thermostatic valve is arranged in the coolant circulating system of an internal combustion engine to control the coolant flow from the internal combustion engine through a direct return flow line and/or through a heat exchanger back to the internal combustion engine. The valve disk supported on the working element housing forms a portion of a valve controlling fluid flow to the heat exchanger.
The present invention provides all the advantages of simplicity and responsiveness to external parameters of the invention described in U.S. Pat. application Ser. No. 510,192. However, the manufacturing expenditures are significantly decreased by forming the adjusting mechanism from the working piston and the counterbearing, and the working piston is positively forced into its adjusted position without having to follow the independently adjusted counterbearing. The working piston thus performs an additional function, namely, it is itself a component of the adjusting mechanism.
A further embodiment of the present invention that the working piston includes an external thread and is screwed into the counterbearing, provided with a corresponding internal thread, and that a control element having a rotating drive is connected to the working piston or to the counterbearing. The adjusting mechanism therefore consists only of the working piston and the counterbearing, in which case, the control element is applied directly to one of the two parts. Constructional expenditures therefore are relatively low.
In one embodiment of this, the working piston is connected with the coupling element via a coupling means transmitting the drive rotations and the counterbearing is stationary. In this case, a threaded borehole of a connecting sleeve is provided to be used as the counterbearing. In another of such embodiments, the working piston is held in a means securing it against twisting, and the counterbearing is formed as a nut that is driven by the control element and secured in axial direction. In a further of such embodiments, the working piston has an axial toothing which engages a pinion that also serves as a counterbearing. This pinion is connected to the control element.
In many embodiments of the present invention, small electric motors such as direct current motors or stepping motors, may be provided as the control elements by means of which intermediate positions of the working piston may be adjusted. Alternatively, hydraulic or pneumatic operating control elements may be employed.
In still another embodiment of the present invention, a connecting sleeve with the thermostatic valve, the counterbearing and the control element form a single structural unit. It is thus possible to test the operability of the whole arrangement before mounting into the motor vehicle in the manufacturing plant and to adjust it to the range of the desired opening temperature. This arrangement will then be installed as a structural unit into the coolant circulating system of an internal combustion engine.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.